/*
 * Copyright (C) 2019 Google.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include "util/ralloc.h"

#include "ir3.h"

static bool
is_safe_conv(struct ir3_instruction *instr, type_t src_type,
			 opc_t *src_opc)
{
	if (instr->opc != OPC_MOV)
		return false;

	/* Only allow half->full or full->half without any type conversion (like
	 * int to float).
	 */
	if (type_size(instr->cat1.src_type) == type_size(instr->cat1.dst_type) ||
		full_type(instr->cat1.src_type) != full_type(instr->cat1.dst_type))
		return false;

	struct ir3_register *dst = instr->regs[0];
	struct ir3_register *src = instr->regs[1];

	/* disallow conversions that cannot be folded into
	 * alu instructions:
	 */
	if (instr->cat1.round != ROUND_ZERO)
		return false;

	if (dst->flags & (IR3_REG_RELATIV | IR3_REG_ARRAY))
		return false;
	if (src->flags & (IR3_REG_RELATIV | IR3_REG_ARRAY))
		return false;

	/* Check that the source of the conv matches the type of the src
	 * instruction.
	 */
	if (src_type == instr->cat1.src_type)
		return true;

	/* We can handle mismatches with integer types by converting the opcode
	 * but not when an integer is reinterpreted as a float or vice-versa.
	 */
	if (type_float(src_type) != type_float(instr->cat1.src_type))
		return false;

	/* We have types with mismatched signedness. Mismatches on the signedness
	 * don't matter when narrowing:
	 */
	if (type_size(instr->cat1.dst_type) < type_size(instr->cat1.src_type))
		return true;

	/* Try swapping the opcode: */
	bool can_swap = true;
	*src_opc = ir3_try_swap_signedness(*src_opc, &can_swap);
	return can_swap;
}

static bool
all_uses_safe_conv(struct ir3_instruction *conv_src, type_t src_type)
{
	opc_t opc = conv_src->opc;
	bool first = true;
	foreach_ssa_use (use, conv_src) {
		opc_t new_opc = opc;
		if (!is_safe_conv(use, src_type, &new_opc))
			return false;
		/* Check if multiple uses have conflicting requirements on the opcode.
		 */
		if (!first && opc != new_opc)
			return false;
		first = false;
		opc = new_opc;
	}
	conv_src->opc = opc;
	return true;
}

/* For an instruction which has a conversion folded in, re-write the
 * uses of *all* conv's that used that src to be a simple mov that
 * cp can eliminate.  This avoids invalidating the SSA uses, it just
 * shifts the use to a simple mov.
 */
static void
rewrite_src_uses(struct ir3_instruction *src)
{
	foreach_ssa_use (use, src) {
		assert(use->opc == OPC_MOV);

		if (is_half(src)) {
			use->regs[1]->flags |= IR3_REG_HALF;
		} else {
			use->regs[1]->flags &= ~IR3_REG_HALF;
		}

		use->cat1.src_type = use->cat1.dst_type;
	}
}

static bool
try_conversion_folding(struct ir3_instruction *conv)
{
	struct ir3_instruction *src;

	if (conv->opc != OPC_MOV)
		return false;

	/* NOTE: we can have non-ssa srcs after copy propagation: */
	src = ssa(conv->regs[1]);
	if (!src)
		return false;

	if (!is_alu(src))
		return false;

	bool can_fold;
	type_t base_type = ir3_output_conv_type(src, &can_fold);
	if (!can_fold)
		return false;

	type_t src_type = ir3_output_conv_src_type(src, base_type);
	type_t dst_type = ir3_output_conv_dst_type(src, base_type);

	/* Avoid cases where we've already folded in a conversion. We assume that
	 * if there is a chain of conversions that's foldable then it's been
	 * folded in NIR already.
	 */
	if (src_type != dst_type)
		return false;

	if (!all_uses_safe_conv(src, src_type))
		return false;

	ir3_set_dst_type(src, is_half(conv));
	rewrite_src_uses(src);

	return true;
}

bool
ir3_cf(struct ir3 *ir)
{
	void *mem_ctx = ralloc_context(NULL);
	bool progress = false;

	ir3_find_ssa_uses(ir, mem_ctx, false);

	foreach_block (block, &ir->block_list) {
		foreach_instr (instr, &block->instr_list) {
			progress |= try_conversion_folding(instr);
		}
	}

	ralloc_free(mem_ctx);

	return progress;
}
